Dislocation Dynamics Simulations

2012 ◽  
Vol 736 ◽  
pp. 13-20 ◽  
Author(s):  
Karri V. Mani Krishna ◽  
Prita Pant
Keyword(s):  
Boundary Conditions ◽  
Strain Hardening ◽  
Deformation Behaviour ◽  
Dislocation Dynamics ◽  
Clear Correlation ◽  
Rigid Boundary ◽  
Rate Of Increase ◽  
Dislocation Densities ◽  
Dynamics Simulations ◽  
Film Substrate

Dislocation Dynamics (DD) simulations are used to study the evolution of a pre-specified dislocation structure under applied stresses and imposed boundary conditions. These simulations can handle realistic dislocation densities ranging from 1010 to 1014 m-2, and hence can be used to model plastic deformation and strain hardening in metals. In this paper we introduce the basic concepts of DD simulations and then present results from simulations in thin copper films and in bulk zirconium. In both cases, the effect of orientation on deformation behaviour is investigated. For the thin film simulations, rigid boundary conditions are used at film-substrate and film-passivation interfaces leading to dislocation accumulation, while periodic boundaries are used for bulk grains of Zr. We show that there is a clear correlation between strain hardening rate and the rate of increase of dislocation density.

Deformation Behaviour of Single Linear Surface Defect Nickel Nanowire at Different Temperatures Studied by Molecular Dynamics Simulations

2020 ◽  
Vol 978 ◽  
pp. 428-435
Author(s):  
Krishna Chaitanya Katakam ◽  
Natraj Yedla
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Surface Defect ◽  
Deformation Behaviour ◽  
Stacking Faults ◽  
Effect Of Temperature ◽  
Dislocation Densities ◽  
Different Temperatures ◽  
Nickel Nanowire ◽  
Dynamics Simulations

The mechanical properties and deformation mechanism of nickel nanowire of dimension 100 Å (x-axis) × 1000 Å (y-axis) × 100 Å (z-axis) containing a single linear surface defect is studied at different temperatures using molecular dynamics simulations. The defect is created by deleting a row of atoms on the surface and is inclined at 25° to the loading axis. The tensile test is carried out at 0.01 K, 10 K, 100 K and 300 K temperature and 108 s-1strain rate. To determine the effect of temperature on the stress-strain curves, fracture and failure mechanism, a thorough investigation has taken place. Maximum strength of 21.26 GPa is observed for NW deformed at 0.01 K temperature and the strength decreased with increase in temperature. Through slip lines, the deformation relief pattern taken place by developing the extrusion areas along with intrusion over the surface defect area in all NWs deformed at respective temperatures. Further it is observed that fracture strains decrease with increase in temperature. After yielding, stacking faults associated with dislocations are generated by slip on all four {111} planes. Different type of dislocations with both intrinsic and extrinsic stacking faults are noticed. Out of all dislocation densities, Shockley partial dislocation densities has recorded a maximum value.

scholarly journals Periodic Boundary Conditions for Dislocation Dynamics Simulations in Three Dimensions

2000 ◽  
Vol 653 ◽  
Author(s):  
Vasily V. Bulatov ◽  
Moon Rhee ◽  
Wei Cai
Keyword(s):  
Boundary Conditions ◽  
Large Scale ◽  
Periodic Boundary ◽  
Periodic Boundary Conditions ◽  
Dislocation Dynamics ◽  
Three Dimensions ◽  
Translational Invariance ◽  
Timing Data ◽  
Dynamics Simulations ◽  
Consistent Treatment

AbstractThis article presents an implementation of periodic boundary conditions (PBC) for Dislocation Dynamics (DD) simulations in three dimensions (3D). We discuss fundamental aspects of PBC development, including preservation of translational invariance and line connectivity, the choice of initial configurations compatible with PBC and a consistent treatment of image stress. On the practical side, our approach reduces to manageable proportions the computational burden of updating the long-range elastic interactions among dislocation segments. The timing data confirms feasibility and practicality of PBC for large-scale DD simulations in 3D.

scholarly journals Boundary conditions for dislocation dynamics simulations and stage 0 of BCC metals at low temperature

2001 ◽  
Vol 677 ◽  
Author(s):  
Meijie Tang ◽  
Ladislas P. Kubin
Keyword(s):  
Low Temperature ◽  
Dislocation Density ◽  
Boundary Conditions ◽  
Dislocation Dynamics ◽  
Body Centered Cubic ◽  
Density Evolution ◽  
Bcc Metals ◽  
Effective Boundary ◽  
Effective Boundary Condition ◽  
Dynamics Simulations

ABSTRACTIn order to study the dislocation density evolution of body centered cubic (bcc) crystals at low temperature by dislocation dynamics (DD) simulations, we investigated carefully three different boundary conditions (BC) for DD, i.e., the quasi-free surface BC, the flux-balanced BC, and the periodic BC. The latter two BCs can account for the dislocation loss from the boundary of the finite simulation box. PBC can also eliminate the influence of surfaces and improve the line connectivity. We have found that the PBC provides a convenient and effective boundary condition for DD simulations and have applied it to the study of dislocation density evolution of bcc metals during stage 0 deformation at low temperature.

scholarly journals Large-scale dislocation dynamics simulations of strain hardening of Ni microcrystals under tensile loading

2019 ◽  
Vol 164 ◽  
pp. 171-183 ◽  
Author(s):  
S.I. Rao ◽  
C. Woodward ◽  
B. Akdim ◽  
E. Antillon ◽  
T.A. Parthasarathy ◽  
...  
Keyword(s):  
Strain Hardening ◽  
Large Scale ◽  
Tensile Loading ◽  
Dislocation Dynamics ◽  
Dynamics Simulations

scholarly journals On the three-dimensional spatial correlations of curved dislocation systems

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Joseph Pierre Anderson ◽  
Anter El-Azab
Keyword(s):  
Correlation Function ◽  
Slip System ◽  
Correlation Functions ◽  
Mean Field ◽  
Coarse Graining ◽  
Dislocation Dynamics ◽  
Coarse Grained ◽  
Spatial Correlation Function ◽  
Line System ◽  
Dislocation Densities

AbstractCoarse-grained descriptions of dislocation motion in crystalline metals inherently represent a loss of information regarding dislocation-dislocation interactions. In the present work, we consider a coarse-graining framework capable of re-capturing these interactions by means of the dislocation-dislocation correlation functions. The framework depends on a convolution length to define slip-system-specific dislocation densities. Following a statistical definition of this coarse-graining process, we define a spatial correlation function which will allow the arrangement of the discrete line system at two points—and thus the strength of their interactions at short range—to be recaptured into a mean field description of dislocation dynamics. Through a statistical homogeneity argument, we present a method of evaluating this correlation function from discrete dislocation dynamics simulations. Finally, results of this evaluation are shown in the form of the correlation of dislocation densities on the same slip-system. These correlation functions are seen to depend weakly on plastic strain, and in turn, the dislocation density, but are seen to depend strongly on the convolution length. Implications of these correlation functions in regard to continuum dislocation dynamics as well as future directions of investigation are also discussed.

Computer-Generated Structural Models for a-Si:H

1988 ◽  
Vol 141 ◽  
Author(s):  
Laurent J. Lewis ◽  
Normand Mousseau ◽  
FranÇois Drolet
Keyword(s):  
Molecular Dynamics ◽  
Boundary Conditions ◽  
Amorphous Silicon ◽  
Periodic Boundary ◽  
Hydrogenated Amorphous Silicon ◽  
Structural Models ◽  
Periodic Boundary Conditions ◽  
Dynamics Simulations ◽  
Hydrogenated Amorphous ◽  
Good Agreement

AbstractA new algorithm for generating fully-coordinated hydrogenated amorphous silicon models with periodic boundary conditions is presented. The hydrogen is incorporated into an a-Si matrix by a bond-switching process similar to that proposed by Wooten, Winer, and Weaire, making sure that four-fold coordination is preserved and that no rings with less than 5 members are created. After each addition of hydrogen, the structure is fully relaxed. The models so obtained, to be used as input to molecular dynamics simulations, are found to be in good agreement with experiment. A model with 12 at.% H is discussed in detail.

Plastic Ploughing of a Sinusoidal Asperity on a Rough Surface

2015 ◽  
Vol 82 (7) ◽  
Author(s):  
H. Song ◽  
R. J. Dikken ◽  
L. Nicola ◽  
E. Van der Giessen
Keyword(s):  
Friction Stress ◽  
Dislocation Dynamics ◽  
Two Dimensional ◽  
Unit Process ◽  
Contact Models ◽  
Self Similar ◽  
Dynamics Simulations ◽  
Micrometer Scale ◽  
Edge Dislocations ◽  
Flat Contact

Part of the friction between two rough surfaces is due to the interlocking between asperities on opposite surfaces. In order for the surfaces to slide relative to each other, these interlocking asperities have to deform plastically. Here, we study the unit process of plastic ploughing of a single micrometer-scale asperity by means of two-dimensional dislocation dynamics simulations. Plastic deformation is described through the generation, motion, and annihilation of edge dislocations inside the asperity as well as in the subsurface. We find that the force required to plough an asperity at different ploughing depths follows a Gaussian distribution. For self-similar asperities, the friction stress is found to increase with the inverse of size. Comparison of the friction stress is made with other two contact models to show that interlocking asperities that are larger than ∼2 μm are easier to shear off plastically than asperities with a flat contact.

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